1. Field of the Disclosure
The disclosure relates to a pixel array module and a test method thereof. Particularly, the disclosure relates to a pixel array module with a self-test function and a method thereof.
2. Description of Related Art
FIG. 1 is a schematic diagram of a conventional three-dimensional (3D) stacked image sensor. Referring to FIG. 1, the 3D stacked image sensor 100 has a development potential due to characteristics of high resolution and high bandwidth. A structure of the 3D image sensing chip includes a pixel array 110 of a top layer, an analog-to-digital converter (ADC) array 120 of a second layer and an image processor array 130 of a third layer, where the components of each layer are stacked through 3D stacking elements 140. The chips of each layer have to be tested before stacking, so as to pick out good chips for a post stacking process. In this way, a yield of the stacked chips may be enhanced, and manufacturing cost may be reduced.
However, when the pixel array 110 of the top layer is tested before the stacking, that a pixel photosensitive signal cannot be read is encountered since in the structure of the 3D image sensor 100, the pixel array 110 of the top layer generates an analog voltage signal after sensing light, and such signal has to be read out by the ADC array 120 of the second layer. However, before the chips are stacked, the voltage signal of the pixel array 110 cannot be read by the ADC 120 of the second layer, and once the voltage signal of the pixel array 110 cannot be read, the test on the layer of the pixel array cannot be performed. When the untested chips are stacked, a yield of the chip stacking may be decreased.